I have to agree, make sure they know your alpha. I have 2 females < 1 yr apart and they've had some issues as well. Both females want to be dominant. Basically I make sure neither get that impression. They're fed at the same time, and I'm careful never to give either of the girls a treat before the others. (I have 4 dogs, but my 2 boys could care less). The girls play, even sleep back to back at times, but I've seen then go for eachother throats before. Basically if there is even the hint of a stare down, growling or posturing I stop it immediately. Usually a stern voice saying their name is enough, they've learned that while they are fighting for the top spot I have the top spot so they usually respond instantly. If it continues then I usually give them a distraction, toy, rawhide whatever. It sounds like your Dobi respects your alpha position, but not you bulldog since the Dobi backs down but the bulldog doesn't. Working with that be careful not to let either of them think they're alpha over you.